1. Field of the Invention
The present invention relates to an expandable multilayer tubular structure intended to be used as a stent, comprising at least two layers firmly attached to each other, and also to a process for manufacturing it.
It has been known for many years to use implantable devices for the treatment of certain diseases in humans or animals. Thus, such a device has been partly or completely inserted into the esophagus, the trachea, the colon, the vascular system, the urinary tract, etc. In the vascular system, when it is desired to introduce such a device, usually called a stent, we require a catheter, a balloon and a filiform guide or the like.
2. Description of the Related Art
The device, when it is positioned at the place where the treatment has to be carried out, extends radially in order to support the vessel walls. Depending on the desired treatment, the stent must remain in place or be removed after the period of treatment. Certain stents that remain in place are provided with a medicinal product that must diffuse over a certain period of time so as, on the one hand, to treat the lesion and, on the other hand, to remedy the lesions that may occur by the fact that the vessel, upon inserting the stent, has been disturbed. The stent, especially one that has to remain inside the tube, must have certain almost contradictory mechanical properties, namely it has to be small, lightweight and, above all, after having been radially relaxed, it must withstand the pressure of the walls of the vessel or tube inside which it is placed, without collapsing. It is therefore necessary, on the one hand, for it to be sufficiently rigid and strong, radially, in order to prevent inopportune collapse and, on the other hand, it must be able to be expandable so that it occupies the place that is necessary for the treatment inside the human or animal vessel or tube.